It is well known in the art that carbon black can be produced by pyrolytic decomposition of various hydrocarbon feedstocks. The widest use of such carbon blacks is in tires as a reinforcing agent for rubber. The presence or absence of carcinogenic materials in very low quantities does not constitute a problem in these applications.
If, however, carbon black is to be used either as a food ingredient or in applications where it gets in contact with food, such as in wrapping materials, rubber hoses, or plastic pipes that come into contact with food materials or ingredients for food, the product is subject to rigid controls and has to pass certain tests before its use in these applications is approved. One of the problems is that extremely small but still detectable quantities of condensed aromatics can be present in carbon blacks. Benzo (a) pyrene is an example of a known carcinogen among the many condensed aromatic ring structures. It would thus be desirable to have a process available by which a carbon black being essentially free of such materials, in particular being free of benzo (a) pyrene can be produced.